Passivation Stainless Steel Casting: Aerospace Guide
TL;DR: Passivation stainless steel casting is a chemical treatment that removes free iron and boosts the chromium-oxide layer, giving aerospace castings full corrosion resistance. It follows AMS 2700 using nitric or citric acid.
Passivation stainless steel casting is the finishing step that unlocks corrosion resistance in flight-critical parts. Done to AMS 2700, passivation stainless steel casting removes surface iron and strengthens the passive layer. It follows our investment casting and machining.
What Is Passivation of a Stainless Steel Casting?
Passivation is a chemical treatment that removes free iron and contaminants from a stainless surface and enhances the natural chromium-oxide film. This restores and maximises corrosion resistance after machining and handling. It is essential on aerospace stainless parts where corrosion cannot be tolerated. See this reference.
Passivation Aerospace Castings and AMS 2700
For passivation aerospace castings, AMS 2700 is the governing specification. Passivation aerospace castings must follow AMS 2700, which defines nitric (Method 1) and citric (Method 2) acid processes and testing.
Key passivation facts:
- AMS 2700: the aerospace passivation specification.
- Method 1: traditional nitric acid passivation.
- Method 2: safer citric acid passivation.
- Removes free iron left by machining and tooling.
- Enhances the chromium-oxide passive layer.
Nitric vs Citric Passivation
The nitric vs citric passivation choice is about safety and performance. In nitric vs citric passivation, nitric is traditional and widely qualified, while citric is greener, safer, and works at lower temperatures.
How the two methods compare:
- Nitric acid: traditional, effective, widely qualified.
- Citric acid: greener, safer, lower disposal cost.
- Both meet AMS 2700 and ASTM A967.
- Citric works at lower temperatures and concentrations.
- The choice depends on the alloy and customer spec.
Passivation as a Corrosion Protection Casting Finish
Passivation is the final corrosion protection casting finish for stainless parts. As a corrosion protection casting finish, it leaves a clean, uniform passive layer ready for demanding aerospace service. This protects the part through years of corrosive exposure.
- 17-4 PH and 15-5 PH aerospace castings.
- 316 stainless components for corrosive service.
- Flight-critical fittings and structural parts.
- Any stainless part needing maximum corrosion resistance.
Why Choose Uni Tritech for Passivation
Uni Tritech is a NADCAP-certified, AS9100D foundry approved by Airbus and Collins Aerospace. We passivate stainless castings to AMS 2700 with full traceability, backed by in-house NDT and laboratory services.
- AMS 2700 passivation to customer specification.
- NADCAP-accredited NDT and laboratory services.
- AS9100D quality, Airbus and Collins approved.
- Full traceability from melt to finished part.
Frequently Asked Questions
Passivation stainless steel casting removes free iron and contaminants left by machining and tooling, and strengthens the chromium-oxide layer. Without it, aerospace stainless parts can rust and pit in service.
Both meet AMS 2700 and ASTM A967. Citric acid is safer, greener, and works at lower temperatures, while nitric is traditional and widely qualified. The choice depends on the alloy and customer spec.
It is a chemical treatment, usually nitric or citric acid, that removes free iron and enhances the passive chromium-oxide film, restoring full corrosion resistance without removing significant metal.
Passivation aerospace castings are stainless flight parts treated to AMS 2700 to maximise corrosion resistance. The spec defines nitric and citric methods and the tests the finished parts must pass.
Yes. Passivation is the final corrosion protection casting finish for stainless castings, leaving a clean, uniform passive layer that resists rust and pitting in demanding service.
Need passivation stainless steel casting to AMS 2700? Contact Uni Tritech to discuss your components.
Need passivated aerospace stainless castings?
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